Glaucodot
General
Category	mineral
Chemical formula	(Co,Fe)AsS (Co0.75Fe2+0.25AsS)
Identification
Molar mass	165.15
Color	Grayish tin white, Reddish silver white
Crystal habit	Massive - Uniformly indistinguishable crystals forming large masses.
Crystal system	Orthorhombic (2/m 2/m 2/m) Space Group: C mmm
Cleavage	None
Fracture	Brittle - Uneven - Very brittle fracture producing uneven fragments.
Mohs scale hardness	5
Luster	Metallic
Streak	black
Specific gravity	5.9 - 6.01, Average = 5.95
Ultraviolet fluorescence	inert
Other characteristics	Nonmagnetic, non-radioactive

Glaucodot is a cobalt iron arsenic sulfide mineral with formula: (Co,Fe)AsS. The cobalt:iron(II) ratio is typically 3:1 with minor nickel substituting. It forms a series with arsenopyrite (FeAsS). It is an opaque grey to tin-white typically found as massive forms without external crystal form. It crystallizes in the orthorhombic system. The locality at Vastmanland, Sweden has rare twinned dipyramidal crystals. It is brittle with a Mohs hardness of 5 and a specific gravity of 5.95. It occurs in high temperature hydrothermal deposits with pyrrhotite and chalcopyrite. Glaucodot is classed as a sulfide in the arsenopyrite löllingite group.

Glaucodot was first described in 1849 in Huasco, Valparaíso Province, Chile. Its name originates from the Greek γλανκός ("blue") in reference to its use in the dark blue glass called smalt.

[edit] References

• Webmineral:Glaucodot
• Mindat with location data
• Scandinavian mineral gallery
• Hurlbut, Cornelius S.; Klein, Cornelis, 1985, Manual of Mineralogy, 20th ed., p. 288, ISBN 0-471-80580-7

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